A History of Cabling for Communications

The history of telecommunications spans slightly more than 150 years, starting with the development of the telegraph in the early 19th century. Telegraphy gave man the means to transmit a series of impulses that represented letters, called Morse Code for Samuel F. B. Morse, who is credited with the invention of telegraphy. When these letters were received and decoded, they provided a way to convey messages over long distances.

 

Naturally, the next step was to consider whether sound might also somehow be electrically transmitted. Alexander Graham Bell applied for his patent for an "electrical speaking telephone" in 1876, beating Elisha Gray by only a few hours. In reality, many people contributed to telephone improvements including Thomas Alva Edison, Lars Ericsson and  David Edward Hughes whose invention of the microphone became universally used in telephones.

 

It is amazing how quickly the use of the telephone spread. The first switchboard, an experiment, was installed in Boston in 1877. Just four years later, there were 54,000 telephones in the United States! The first connections from Boston to New York begain in 1884. Wireless communications developed from the work of Nikola Tesla and Guglielmo Marconi. In the first decade of the 20th century, Dr. Lee deForest's invention of the vacuum tube amplifier enabled long distance communications.

 

Technology allowed the expansion of telecommunications. With the advent of the space program in the 1960s, communications satellites expanded the worldwide telecommunications network faster than could be done by laying transoceanic cables. By the 1970s, integrated circuit technogy and the microprocessor began to influence telecommunications and computers. Experiments began in digital voice transmission and fiber optics. Computer networks like Ethernet and the predecessor of the Internet were developed.

 

The 1980s brought wide scale use of digital telecom, computer networks and fiber optics, but was also the era of the breakup of the Bell system. Users who once depended on AT&T for telecom standards and IBM or other computer companies for the "rules" they depended on were left stranded.

 

Manufacturers assumed responsibility for standards development to ensure interoperability of their products - under the auspices of the IEEE for computer networking electronics and EIA/TIA for cabling in the US and ISO and IEC worldwide. Thus was born the industry standards that we all depend on for today's communications networks.

What Are Cabling Standards?

Widespread useage of any technology depends on the existence of acceptable standards for components and systems. These standards are written as minimum specifications for components and systems that will  ensure interoperability of equipment from various manufacturers. The most important "standard" and the only one that is legally mandatory is the National Electrical Code developed by the National Fire Protection Assn. that covers all aspects of electrical and fire safety. Article 800 of the NEC covers communication circuits, such as telephone systems and outside wiring for fire and burglar alarm systems and Article 770 covers fiber optics. Also, all VDV wiring must comply with building and electrical codes applicable in your state or city.

 

But during the 1980s, technology changed rapidly. Phone signals became digital, fiber proliferated, PCs became connected over LANs and new cables and cabling architecture were needed. The goal was to make buildings "smart," able to allow computer and phone conversations over a standardized wiring system. By the early 90s, a scheme of "structured cabling" was standardized by technical committee of a trade association, the merged Electronic Industries Association and Telecommunications Industry Association (hereafter referred to as EIA/TIA) in the USA and ISO/IEC worldwide.

 

This cabling standard, developed by what was then called the EIA/TIA TR 41.8 committee - now renamed TR 42 - is referred to by the number of the primary standard, EIA/TIA 568, although there are actually a number of standards, technical advisories, etc. that cover all aspects of structured cabling. When most people simply say "568" when they mean the entire output of the TR 42 committee (see below.)

 

Many people think this standard is a mandatory, even legal, document like the NEC. In fact, "568" is a voluntary interoperability standard for communications cabling, developed by a number of manufacturers of cabling components and networking equipment, so that they might make equipment that could use any 568-compliant cabling system and be upgraded in the future as long as it was designed for the same cable plant. What 568 is, in fact, is a common sense approach to cabling that defines component and cabling system specifications and offers interoperability, upgradability and low cost due to the numerous manufacturers offering compatible products. 

 

Note: TIA-568 is a US standard. Worldwide, ISO/IEC 11801 is the international standard. ISO/IEC writes these standards and a summary of their standards is below.

The Basics of "568"

The TIA "568" structured cabling standard calls for connecting the desktop (work area) to a telecom closet (the "horizontal" run) with up to 100 meters of cable (including 90 m of permanently installed cable (permanent link) and no more than 10 m total of patchcords), which is usually unshielded twisted pair - UTP - with 4 pairs of wires - called Cat 3, Cat 5, Cat5e, Cat 6 or Cat 6A. The "Cat" or "category" designation refers to a performance level or grade for UTP cabling, which we will explain in the Cables section. Most copper installations today use Cat 5e or Cat 6 exclusively, as they aren't that much more expensive than Cat 3 and can support phones or any LAN on any outlet. Screened twisted pair (foil shielded over the 4 pairs) and shielded twisted pair (STP) are also acceptable and in fact widely used outside the USA.

 

 

The backbone cabling can be either UTP or fiber optics. In larger networks, fiber is most often used for its longer distance capability and higher bandwidth. 568 specifies two multimode fibers, 62.5/125 - the most common MM fiber until recently, and 50/125 - a higher bandwidth fiber rated for use with lasers for gigabit networks that is rapidly overtaking 62.5/125 in popularity. Singlemode fiber is also specified for longer backbone links, as in a campus, for high speed networks.

 

Fiber optics is also a horizontal option in 568, but not often used because of the higher cost except where high bitrate networks or future upgrades are expected. However, a properly designed centralized fiber network that connects the desktop directly to the computer room with no intermediate electronics does not need a telecom closet and saves the cost of conditioned power, data ground, AC and the floor space, which may offset the additional cost of the fiber electronics.

 

Virtually every corporate network now includes wireless, which is, of course, not wireless since access points are connected into the network with copper or fiber cabling. Issues for wireless include proper siting of the wireless access points (antennas, also abbreviated as APs), providing adequate bandwidth to the access points and ensuring network security since wireless signals are easily intercepted.

The telecom closet, or telecom room (TR) as it is now called, houses the hubs for the computers in the work areas. These hubs are interconnected on "backbone" wiring which is mostly fiber optics, as it usually carries higher speed signals over longer distances and provides isolation from ground loops, another problem with copper cabling in LANs. The main cross-connect (MXC) or equipment room contains the network and telco hardware. For the telephones, their lower bandwidth requirements allow longer runs, so they are usually simply connected to backbone cables in the telecom closet with a punchdown and run straight to the MXC.

 

TIA 568 standards have also included IBM Type 1 cable, a shielded two pair cable, since it is still used in some networks. However, it does not include coax cable, like RG-58 used in some Ethernet LANs and RG-6 used in CATV and CCTV, except in the residential standard.

 

Beyond "568"

568 is only part of the structured cabling standards. It's a multi-part standard itself and there are several more standards cover other areas of cabling:

EIA/TIA 568: The main standard document for structured cabling, usually referred to as simply "568." Always check with manufacturers for the latest revisions.

EIA/TIA 569: Covers pathways and spaces. Defines the "telecom closet" or telecom room as it is now called.

EIA/TIA 570: Residential cabling.

EIA/TIA 606: Cabling system administration (documentation)

EIA/TIA 607: Grounding and bonding

 

 

International Standards

The international equivalent of EIA/TIA 568 which came later and basically copied 568 is ISO/IEC 11801. The standards are written similarly to what has been done by TR 42. Here are their relevant standards:

ISO/IEC 11801 - Cabling for customer premises - structured cabling similar to TIA 568
ISO/IEC 14763-1 - Administration, documentation - similar to TIA 606
ISO/IEC 14763-2 - Planning and Installation - similar to TIA 569
ISO/IEC 14763-3 - Testing optical fibre cabling - included in TIA 568
IEC 61935-1 - Testing copper cabling - included in TIA 568

The "Cables" of "Cabling"

The choice of  cable in network cabling (or communication medium as it is sometimes called) is rather important because of the extremely high frequencies of the signals. Sending a 60-cycle utility power through a wire rarely presents a difficulty; but sending a 1 or 10 billion bits per second signal can be a lot more difficult. For this reason, the method of sending signals and the materials they are sent through can be important.

 

 

Network Cabling Types

A number of cabling options have been developed over the history of communications and are still in use for networking connections.

 

Unshielded Twisted pair (UTP) - UTP cable is the primary cable used for networks, as specified in the EIA/TIA 568 standard. UTP was developed from the original phone wires but refined to enhance its bandwidth capability. This cable type has been widely used because it is inexpensive and simple to install. The limited bandwidth of early UTP (which translates into slower transmissions) has pushed development of new cable performance grades (the "categories" of 568) but has created a more expensive product and more complicated installation process.

 

Screened Twisted pair (ScTP) - Same as UTP with an overall shield around the 4 pairs. While not currently specified for any networks or covered in the EIA/TIA 568 standard (but not prohibited), it is used in many networks in Europe where EMI is a greater concern. It tends to be more expensive, harder to terminate and requires special shielded plugs and jacks.

 

Shielded Twisted Pair (STP) - Like UTP but with a shield around every pair. Widely used in IBM systems (IBM Type 1 cable) and included in early versions of 568.

 

Coaxial Cables - The original Ethernet cable was coax and coax is still used in video (CCTV, CATV) systems. This is familiar and easy to install, has good bandwidth and lower attenuation but more expensive and bulky. Not included in 568, but in 570 for residential video use. Coax is also used in residential applications for LANs using a transmission scheme called MoCA that works like a cable modem. Read more on coax. 

 

Optical Fiber - Optional for most networks, top performance, excellent bandwidth, very long life span, excellent security but slightlly higher installed cost than twisted pair cables, more expensive electronics interface to them. Fiber can be cost efffective with optimal architecture. See FIber in Premises Cabling and the FOA Online Guide Table of Contents .

 

Other Transmission Options

Wireless - no data transmission cables are required to connect any individual terminal, but wireless requires cabling to every antenna (called an Access Point.) Within the range of the radio signals, a terminal can be moved anywhere. Usually wireless is more expensive but can be used in locations where is would be difficult to install cables. In the modern network, wireless is a requirement because so many users want "mobility" - so they are not "tethered" to a desktop. More on wireless. 

 

Infrared Transmission - Also transmits data without wires or fibers using infrared (IR) light but each transmitter requires cabling. By sending pulses of infrared light in the same patterns as electronic pulses sent over cables, it is possible to send data from one place to another. Networks based on IR transmission have been developed for use in office and for line-of-sight transmissions between buildings. It is generally limited in range and can be interrupted by blocking or weather.

 

Powerline or Phone Line Transmission - Networks using available power line cabling have been under development for many years, but  with mixed results due the unpredictability of wiring performance and interference from power line noise.

 

Overview of Premises Cabling and Standards  
Jargon  
Networks
UTP Cables  
UTP Terminations,  (Tutorial). UTP Termination.   
UTP Installation VHO  66 Block, 110 Block, Jacks, Plugs  
UTP Testing,  UTP Wiremapping  
Coax Cable  VHO Coax Termination  
Fiber Optics in Premises Cabling
Wireless
Design, New T-568-C Nomenclature
Premises Cabling Installation
Glossary

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